Specification for GRUNDFOS AMD - wastewater pumps
Requirements
Provide ______direct drive mixer/s. Each mixer shall have a stainless steel propeller with a maximum rotating speed of ____ rpm and a maximum diameter of _____ inches. The mixer/s shall have a 460 volt, three (3) phase motor providing a maximum shaft power of _____ Hp. Minimum thrust capabilities shall not be less than ______ft. lbs.
The mixer/s shall be supplied complete with all mounting assemblies that are completely assembled and delivered to the jobsite without requiring assembly by the contractor. This is required to insure complete compliance with specified materials and to insure warranty issues are borne only by the mixer supplier.
Mixer Design
The mixer shall be of direct drive design without the need for gears. It shall be easily removed for inspection and service without the need for personnel to enter the tank or pit in which it is installed. This shall be accomplished by a manufacturer supplied complete mixer mast assembly that shall be an integral part of the mixer scope of supply.
Each mixer shall be supplied with electric power / control cable of a length required for installation plus a length of 10 feet for maintenance purposes. The power/control cable shall be resistant to oil, corrosive gases, or other material normally found in the application as specified. Provide SS cable holders with the supplied mixer mast assembly as necessary to provide cable strain relief as required.
Mixer Construction
All major casings coming into contact with the mixed media shall be of Stainless Steel with smooth surfaces and devoid of irregularities. The propeller and all fasteners shall also be of stainless steel. The propeller shall be dynamically balanced, and non-clogging. The propeller shall be capable of handling fibrous materials and other matter as normally found in the specified application. The mixer shall incorporate a guide bracket of a non-corrosive polyamide or stainless steel material. Lesser materials are not acceptable.
The motor shaft shall be of stainless steel and rotate on two permanently lubricated bearings. Bearings shall be designed for long service life at full load requirements. The outer seal shall be at minimum a mechanical seal with faces of silicon carbide, both faces. Seals shall require neither maintenance nor adjustment but shall be easily accessible and replaceable.
Mixer Motor
Motors shall be provided as an integral part of the mixer design. Motors shall be suitable and fully capable of operation with PWM variable frequency drives and shall be non-overloading across the full performance range of the mixer. The motors service factor shall be at minimum 1.10 and be capable of at minimum 20 starts per hour. Motors shall be capable of withstanding all forces which may be imposed during the course of normal operation be of asynchronous in design. The motor shaft shall be of at minimum Type 316 stainless steel.
Protection
The mixer motor shall be furnished with protective devices as normally provided by the pump manufacturer. These devices shall be monitored by a manufacturer built relay status module. The motor shall be provided with thermal sensors embedded in each winding to provide motor over-temperature protection. A water-in-oil leakage sensor shall be installed within the oil chamber to monitor the amount of water in the oil. In this way, operations personnel can monitor seal leakage without having to remove the pump from service.
Mixer Mast Assembly
Each mixer shall be supplied with its own mixer mast assembly per contract drawings. A removable turning handle shall be provided for each mast to permit manual adjustment of the mixer’s horizontal attitude. The mast shall be minimum 2” x 2” square tube with 1/8” wall, supplied with factory welded sockets at the top, bottom and at intermediate levels as needed to provide support at a maximum of 10ft intervals.
Sockets shall be lined with a kynarâ insert to insure easy mast rotation, and shall work in conjunction with supplied mounting brackets to secure the unit to the tank wall. The top mast bracket shall include a rotary positioning plate which allows the mast to be secured in any of 14 locations with a total of 167 degrees of rotation. Wall extension brackets, if required, shall be provided with the mast and shall be custom designed to insure a straight and true installation.
A fabricated mixer support frame (an integral part of the mixer and guide mast assembly system) shall support the entire weight of the mixer at its horizontal center of gravity. The frame shall include a bracket with stainless steel or nylon liners for attachment to the mast. A static cable with adjustable end loop shall be furnished to support the mixer at various operating levels; as-well-as; a permanently mounted stop on the mixer mast to insure the mixer cannot be operated to a level below which improper or damaging operation could occur.
Portable Lifting Hoist and Lifting Cable
Each mixer mast assembly shall be provided with one (1) portable hoist with a fixed reach for each mixer in this section. The hoist shall be designed to be mounted on the top mast mounting bracket. It shall include a manual brake winch, and shall be adequately rated to lift the mixer and support arm off the mast and directly onto the adjacent deck surface. If handrail is fitted to the deck, removable sections or safety chain sections shall be provided such that the mixer does not need to be lifted over the handrail. A Type 316 stainless steel lifting cable, permanently attached to each mixer, shall be provided in sufficient length for attachment of the upper end to the winch cable reel when the davit assembly is installed.
Quality Control
Prior to shipment, the mixer manufacturer shall check each unit for proper balance and alignment, quiet vibration-free operation, proper electrical characteristics, and satisfactory performance. The mixer manufacturer shall perform certified performance tests in accordance with ANSI/ISO Standards to insure that the performance of the supplied units is in accordance with specified requirements. These tests results shall be certified by the mixer manufacturer and submitted to the engineer for approval prior to shipment. The engineer and owner reserve the right to inspect these tests.
Verification of Performance
All mixers shall be field tested after installation to demonstrate satisfactory operation without excessive noise, vibration, or overheating. Any mixer which fails to meet any of the contract specifications will be modified, repaired or replaced by the contractor at no additional cost to the owner.
Date: 2011-01-01
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